[libvirt] i want to update the disk driver from ide to virtio, but fail , why ?

[Cole Robinson]

On 12/20/19 6:23 AM, thomas wrote:
> hi, ALL:
> my question description as follow:
> 
> 
> 
> virsh dumpxml root-vsys_v2  > v2.xml ,  
>  in the v2.xml has the following information:
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='qcow2'/>
>       <source file='/home/root-vsys_v2.qcow2'/>
>       <backingStore/>
>       <target dev='hda' bus='ide'/>  *// i want change the 'ide' to
> 'virtio', but fail*
>       <alias name='ide0-0-0'/>
>       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>     </disk>
> 
> so i create a new xml name v2-new.xml ,it content is:
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='qcow2'/>
>       <source file='/home/root-vsys_v2.qcow2'/>
>       <target dev='vda' bus='virtio'/>
>     </disk>
> 
> then run:
> virsh update-device root-vsys_v2 /root/v2-new.xml  --live
> the result is:
> [root at NSG ~]# virsh update-device root-vsys_v2 /root/v2-new.xml  --live
> error: Failed to update device from /root/v2-new.xml
> error: internal error: No device with bus 'virtio' and target 'vda'
> 

Hi Thomas. update-device can not be used to change from IDE to virtio
for an existing device. update-device can only be used for changing
certain parameters of an existing device on the live VM, but changing
IDE to virtio is effectively an entirely different device. The closest
you can possibly get is trying to detach-device the existing disk, then
attach-device the virtio disk, but IDE doesn't support hotplug so the
detach step won't work

- Cole